Articulation apparatus for external fixation device

ABSTRACT

An articulation element consisting of a plurality of adjustable jaw pairs for the purposes of fixating the relative position of coupled bars and/or bone pins of an external bone fixator. Each of the adjustable jaws consists of a pair of hemispherical jaw elements contained within a spherical housing. A passage is eccentrically arranged through the jaw elements to accept the pin or bar. The jaw elements have interposed between them a spring element that serves to bias the jaw elements in the closed position. Pins serve to provisionally lock the jaw elements in the closed position. Spring loaded buttons act to release the pins thereby allowing the jaw elements to open accepting the pin or bar. The jaws are attached in a back to back fashion through the use of a threaded collar which acts as a turnbuckle pulling the jaws together when tightened.

CLAIM OF PRIORITY

This application is a continuation of U.S. patent application Ser. No.13/721,199, filed Dec. 20, 2012, which is a continuation of U.S. patentapplication Ser. No. 13/038,103, filed Mar. 1, 2011, (now U.S. Pat. No.8,361,073), which is a continuation of U.S. patent application Ser. No.12/727,533, filed Mar. 19, 2010 (now U.S. Pat. No. 7,938,829), which isa continuation of U.S. patent application Ser. No. 11/708,987, filedFeb. 21, 2007, (now U.S. Pat. No. 7,708,736), which claims the benefitof U.S. Provisional Application No. 60/775,565 filed Feb. 22, 2006,which are all incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

This innovation relates to an articulation element employed in thefixation of cylindrical components, namely bone pins and bar systems,utilized in the field of external fixation.

BACKGROUND OF THE INVENTION

External fixation devices typically include external frames which areused in conjunction with bone pins which are surgically placed into thebone fragments to be repaired or immobilized to promote healing. Suchexternal fixation systems allow for particular placement of the bonepins that hold the bone fragment into which they are inserted, as thereare often characteristics in the affected area that require delicateplacement of pins such as proximity to nerves or arteries, or aroundjoints.

The field of external fixation varies widely comprising many differenttypes of apparatus. Typically bone pins are inserted through the softtissue into the bone fragments; devices are then affixed to the pins andserve to connect the various fragments in such a way as to maintaincorrect anatomic position during the healing process. As is often thecase, placement of the bone pins must be carefully selected to avoiddamaging structures such as blood vessels, nerves, tendons, etc.Additionally consideration must be given to the structural integrity ofthe bone stock in combination with geometric stability considerations ofthe final construct.

Earlier fixation systems required prior assembly (complete or partial).One such know system uses a clamping type articulation element for therelative positioning of fixation bars and bone pins of an externalfixation device. A drawback of such a device is that the articulationelements require being mounted on the fixation bars or the pins viatheir ends in advance of attachment. Until the clamping mechanism insuch device is locked, the components are not held firmly and can movewith respect to one another, making it difficult to hold all componentsin their proper relative orientation prior to or during final locking ofthe device.

Other known external fixation devices have been developed where thecomponents of the external fixation devices are assembled after the pinshave been inserted into the optimum position with respect to the bonefragment to be held and the tissue surrounding them. Typically thefixation bars making up the frame of the fixation device are then placedbetween the bone pins and articulation elements are used to connect thebars and the pins. It is often necessary that these articulationelements allow the bars or pins to be held at variable angles.

To address these concerns while providing maximum utility and ease ofuse; manufacturers have sought to develop fixation devices that allowfor the placement of the bone pins to be independent of the externalsupporting structures that ultimately connect the pins together. Incomplex fractures there is often a need to place many pins, eitherbecause there are many fragments, or due to the poor quality of the boneand/or the nature of the fracture. Many pins, many of which will presentthemselves in different attitudes and inclinations, create a challengewhen it comes time to connect them to the external structure. For thisreason it is imperative to provide as many degrees of freedom whenconstructing an articulation element.

A simple analog to this condition is the case of the simply supportedbeam having more than 2 simple supports. This condition is characterizedas being overly constrained. Unless the beam or the foundation is ofsufficient flexibility it is impossible to share the load evenly acrossall of the multiple supports. To provide a flexible beam would defeat togoal of external fixation; we therefore need to provide a support systemin the way of articulation elements that have the placement flexibilityto evenly support the external structure.

One known prior art system describes an articulation component havingtwo cylindrical joints with a revolute joint interposed between them.The characteristic mobility of this construct is two translations andthree rotations for a total of five degrees of freedom. A known suchsystem describes a similar device with the exception that the interposedrevolute joint is replaced with a spherical joint. The characteristicmobility of this construct is two translations and five rotations for atotal of 7 degrees of freedom. One could argue that more than 6 degreesof freedom is redundant and to some extent that is true but these extradegrees of freedom, redundant or not, make the placement of the devicemore flexible. This added spherical joint does however come at someexpense, namely the pin to bar centerline distance must be increased,which makes for a bulkier construct while at the same time increasingthe moment loading on the joints themselves.

The foregoing is believed to describe prior art systems as set forth,for example, in U.S. Pat. Nos. 6,080,153 and 7,048,735 (so called Jet-XUnilateral Fixation System), and EP 0321472.

SUMMARY OF THE INVENTION

The present invention provides advancements in the state of the relevantart by, inter alia, providing a an articulation element employed in thefixation of cylindrical components, namely bone pins and bar systems,utilized in the field of external fixation.

In accordance with one aspect of the present invention, the presentinvention aims to provide greater placement flexibility in a morecompact construct than is presently available. It comprises theplacement of fixation elements on either side of a fracture. Thesefixation elements are commonly referred to as pins, whereby one or morepins are screwed into a bone. One or more pins are located on eitherside of a fracture and connected to a bar via a clamp and/or a clampingsystem. The present invention relates to connecting pins with one ormore bars in order to fixate a fracture. Such bars may also be connectedto other bars or structures, if needed. In connecting pins to rods, itis advantageous to have mobility in a clamping system to allow for easeof placement and/or post placement manipulation.

One illustrative embodiment of the present invention comprises two (2)independent but connected clamp jaws, each clamp jaw being set in aclamp housing. Each clamp jaw comprises two (2) clamp jaw halves. Theclamp jaw halves are shaped such that a clamp jaw is able to open andclose around a bar or pin. In this embodiment of the present invention,the clamp jaw is able to clamp around a bar, while simultaneously, aconnected corresponding clamp jaw is able to pivot about an axis normalto the axis of a pin or bar that is being clamped. Clamp jaw halves maybe circular in shape to surround a pin or bar with a circular crosssection. The clamp jaw halves may also be shaped to correspond to thecross section of the shape of the pin or bar being clamped. In anotherembodiment of the present invention, the clamp jaws may also beconnected such that the clamp jaws also allows a bar or pin to rotateand approximately and/or equal to 20 degrees while clamped to allow forgreater range and ease of positioning.

In alternative embodiments of the present invention, a spring is used tobias each clamp jaw half into the closed and/or clamped position. Eachclamp jaw half is held in place by a jaw pin which engages acorresponding hole. In one embodiment of the present invention, thecorresponding hole may comprise a specially milled shape and/or form.The jaw pins serve to limit the amount of travel of the clamp jaw halvesand to lock the clamp jaw halves into the closed and/or clampedposition. The jaw pins are preloaded into a locked position whereby thejaw pins are engaged with the hole in the jaw halves with a disc spring.The disc spring acts like a pressure plate spring and is made up of aseries of radial levers connected around a periphery. Spring levers holdeach jaw pin in place and allow each jaw pin to come into contact with arelease button. The release button is concentric with the jaw pin andthe disc spring. Application of an axial force on the release buttonscauses retraction of the jaw pins in the opposite direction. Whenpressure is applied to the release buttons, such pressure causes the jawpins to disengage from the clamp jaw halves, allowing the clamp jawhalves to open around the bar or pin. Removal of pressure will cause thejaw pins to re-insert into the holes in the clamp housing and a bar orpin may be placed in the clamp jaws and locked into place. A bar in aclamp jaw is able to rotate and slide about an axis orthogonal to thecorresponding pin axis and pivot about the pin axis.

In the illustrative embodiment of the present invention, two (2) clamphousings are connected to each other by a collar. The collar has aninterior diameter which comprises both a right hand female thread andleft hand female thread. Each clamp housing also comprises acorresponding right male thread and a left male thread which attach theclamp housings to the collar. The clamp housings may be keyed to eachother such that the clamp housings are limited in rotation to 180degrees relative to each other. This prevents the clamp housings fromhaving an unequal thread engagement in the collar and limits unnecessaryrange of motion.

In another embodiment of the present invention, each clamp housing withcorresponding clamp jaw, also comprises two corresponding clutch plateswhich slide along an axis concentric with a collar. The clutch platesare keyed to the clamp housing in which they slide and bear against theclamp jaw halves and corresponding clutch plate. When the collar istightened, the collar forces the clutch plates against each other andforces the clamp jaw halves into a respective clamp housing. The actionlocks the clamp jaw halves to the bar or pin and the clamp housings toeach other fixating the clamping system. In other embodiments of thepresent invention, the clutch plates may be smooth and/or may beserrated.

In embodiments of the present invention for applications with low loadand/or for accommodating less weight, the clutch plates could be smooth.This may be useful for fractures of the upper extremities. In suchembodiment of the present invention directed at low load applications,the clamp jaw halves could comprise a smooth outer spherical surface. Inyet another embodiment of the present invention for applications withhigher load and/or accommodating more weight, the clutch plates could beserrated and/or comprise clamp jaw halves that may comprise a fish scaleand/or textured outer surface. In another embodiment of the presentinvention, a collar and clamp housings may comprise a tapered formand/or threaded diameters, for example, pipe thread, whereby in additionto bringing the two clamp housings together axially, the threadeddiameters would squeeze the clamp bodies radially further tightening andclamping the clamp jaw halves.

Advantages of the present invention comprise the following: the presentinvention allows for one-handed application; includes one lock perjoint; allows for greater degrees of freedom in mounting; allows forgross manipulation; accommodates multiple indications; comprises fewcomponents; and requires minimal training.

It will be appreciated by those skilled in the art that the foregoingbrief description and the following detailed description are exemplaryand explanatory of this invention, and are not intended to berestrictive thereof or limiting of the advantages which can be achievedby this invention. Thus, the accompanying drawings, referred to hereinand constituting a part hereof, illustrate preferred embodiments of thisinvention, and, together with the detailed description, serve to explainthe principles of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional aspects, features, and advantages of the invention, both asto its structure and operation, will be understood and will become morereadily apparent when the invention is considered in the light of thefollowing description of illustrative embodiments made in conjunctionwith the accompanying drawings, wherein:

FIG. 1 is an isometric view of an articulation element according to anillustrative embodiment of the present invention.

FIG. 2 is a second isometric view of the articulation element of FIG. 1.

FIG. 3 is a representation of the articulation element of FIGS. 1 and 2shown in schematic cross section.

FIG. 4 is a close up representation of the articulation element of FIG.3.

FIG. 5 is a cut away view of the release mechanism of the articulationelement of FIGS. 1 and 2.

FIG. 6 is a view of the pin slot in one of the jaw elements of thearticulation element of FIG. 3.

FIGS. 7a and 7b are views of the clutch plate of the articulationelement of FIG. 3, and

FIG. 8 is a perspective view of an illustrative external fixation systemusing the articulation element of the present invention for use on along bone application.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The external fixation system of the present invention includes anarticulation element employed in the fixation of cylindrical components,namely bone pins and bar systems. Its structure and functional detailswill be discussed in detail below in the context of an illustrativeembodiment and with reference to the figures provided.

FIGS. 1 and 2 show isometric views of an articulation element 200according to an illustrative embodiment of the present invention.

The articulation element 200 consists of a pair of back-to-backspherical clamping mechanisms 200A and 200B that act to apply clampingpressure to cylindrical bars and/or pins shown conceptually as 100 and101. The clamping mechanisms themselves consist of a pair of sphericaljaw elements 90 within each of the spherical clamping mechanisms.Release buttons 80 allow the preloaded jaw elements 90 to relax toreceive or release a rod or pin 100. Each mechanism 200A and 200B freelyrotates about axis Z (i.e., in either rotational direction about the Zaxis) as shown by arrows ZA and ZB. Lock ring 60 is used to lock therelative positions of 200A and 200B as will be described in detailbelow.

As shown in FIG. 2, bars 100 and 101 are shown in place in the clampingmechanisms 200A and 200B. Spherical jaw elements 90 (together forming anadjustable jaw pair) are disposed within the clamping mechanisms 200Aand 200B such that they allow elevation of the respective bars mountedtherein. Bar 100, shown mounted within mechanism 200A, can elevatethrough an angle A.degree. about the X axis as shown in FIG. 2. (Whileelevation only about the X axis of bar 100 in mechanism 200A is shown,similar elevation of bar 101 in mechanism 200B through an angleB.degree. about a Y axis (not shown) will be understood. The Y axis isnot necessarily in any predetermined relation to the X axis, for exampleperpendicular to X.).

In further detail and with reference to FIGS. 3-7, the articulationelement 200 consists of a pair of back-to-back spherical clampingmechanisms or members that act to apply clamping pressure to cylindricalbars and/or pins shown conceptually as 100 and 101 (FIG. 4). Theclamping mechanisms themselves consist of a pair of spherical jawelements 90 that are held with in a spherical socket 11 (FIG. 4) withinthe clamp housing 10. Located eccentrically from the spherical jaw, anangular or Gothic arch type passage is machined to form the clamping orfriction surfaces 91 (FIG. 4). Teeth, not shown, could if desired alsobe used on these surfaces 91 to provide a better gripping action.

Spherical jaw elements 90 are preloaded in a clamped or closed positionby interposition of an elastic element 70 between the jaw elements 90,shown here as a coil spring 70. The coil spring 70 is seated within acylindrical pocket 92 in each of the jaw elements 90. The elasticelement 70 serves to bias the jaw elements 90 into the closed or clampedposition around bar element 101. A tang and clevis arrangement betweenthe two jaw elements, shown as a groove 93 (FIG. 4) constrains the jawelements to rotate open and closed in a plane such that the pin and/orbar, 100, 101 can be accepted once pressure is applied to face 94 ofeach jaw element 90 (FIG. 4). Pressure on face 94 acts to open the jawelements 90. Once the pin and/or bar 100, 101 is seated the elasticelement 70 forces the jaw elements 90 to rotate closed.

Pins 20 engage both the clamp housing 10 and the jaw elements 90 andserve to limit the range of mobility of the jaw elements 90 such thatthe mouth of the jaw elements 90 (formed between faces 94 of jawelements 90) does not rotate out of the opening 12 (FIG. 4) of the clamphousing 10 by fitting into the milled recess 95 (FIGS. 4 and 7). Fullyengaged, these pins 20 keep the jaw elements 90 in the closed positionwhile still allowing for the rotation of the jaw elements 90 about theaxis of the pins 20 by fitting into the cylindrical recess 96 (FIGS. 4and 6).

With reference to FIGS. 3, 4 and 5, a single point parallel releasemechanism allows pins 20 are retracted and engaged by means of a button80 and disk spring mechanism 30. The button 80 is guided withincylindrical bore 13 in the clamp housing 10. A cylindrical bore 81within the button 80 accepts and guides the pin 20. A disk spring 30fashioned in such a way as to have a radial array of levers the outerdiameter 32 of which is fitted within a circumferential groove 83 withinthe button 80. The inner diameter 33 of the disk spring 30 engages thepin 20 in circumferential grove 21. Application of force to the button80 acts on the outer diameter 32 of the disk spring 30 which acts as alever pivoting about fulcrum 31 which bears on the clamp housing. Thisaction applies a force opposite in direction to that which was appliedto the button to circumferential grove 21 of the pin 20 causing the pin20 to retract allowing the jaw elements 90 to open in order to acceptthe pin and/or bar 100, 101. Releasing the force on the buttons 80allows the pins to re-engage the cylindrical bore 96 of the jaw elements90 keeping them in the closed position.

Once a pin and/or bar 100, 101 is engaged with both sets of jaw elements90 the pins and/or bars 100, 101 are still free to slide and rotaterelative to the jaw passage 91 while the jaw/pin/bar 90, 100, 101assemblage is allowed to pivot about the pin 20 axis. Additionallyeither half of the articulation element 200 is allowed to rotate up to180 degrees about the axis of lock ring 60.

To fixate the articulation element 200 lock ring 60 is tightened; havingboth a left hand and right hand female thread 61 on the ID it engagesthe corresponding threads on the clamp housing 10 drawing the two halvesof the articulation assembly 200 together. As the two halves cometogether pressure is applied to the clutch plates 40 which bind clutchrings 50 into the corresponding clutch plate 40 on the other side. (Seealso FIGS. 6A and 6B) The pressure effectively keeps one clutch plate 40from rotating relative to the other and the flat sides 42 key into theclamp housing 10. The spherical side 43 of 40 also applies pressure tothe spherical surface of the jaw elements 97 (FIG. 7) wedging the jawelements 90 in the clamp housing 10 which applies clamping pressure tothe pins and/or bars 100, 101.

FIG. 8 shows an illustrative embodiment of the present invention wherethe articulation elements described herein are used in an externalfixation system for a long bone application. Several rods 100 and pins101 are shown being connected via articulations elements 200 of thepresent invention and fixation ring 300. Any number of pins or rods incombination with articulation elements 200 and ring 300 may be used aswill be understood by one skilled in the art.

The present invention has been illustrated and described with respect tospecific embodiments thereof, which embodiments are merely illustrativeof the principles of the invention and are not intended to be exclusiveor otherwise limiting embodiments. For instance, although thedescription provided hereinabove along with the accompanying drawingsillustrate particular embodiments incorporating one or a few features ofthe present invention, those skilled in the art will understand in viewof the hereinabove disclosure that alternative configurations can bedevised and implemented, as well as other designs capable of achievingthe purpose and benefits of the discussed aspects of the invention.

Accordingly, although the above description of illustrative embodimentsof the present invention, as well as various illustrative modificationsand features thereof, provides many specificities, these enablingdetails should not be construed as limiting the scope of the invention,and it will be readily understood by those persons skilled in the artthat the present invention is susceptible to many modifications,adaptations, variations, omissions, additions, and equivalentimplementations without departing from this scope and withoutdiminishing its attendant advantages. It is further noted that the termsand expressions have been used as terms of description and not terms oflimitation. There is no intention to use the terms or expressions toexclude any equivalents of features shown and described or portionsthereof. It is therefore intended that the present invention is notlimited to the disclosed embodiments but should be defined in accordancewith the claims that follow.

What is claimed is:
 1. An articulation device for an external fixationapparatus for treating a patient, the articulation device having alongitudinal axis and comprising: a clamp mechanism defining a socket;an adjustable jaw pair arranged within the socket, the jaw pair beingconfigured to capture a rigid element of the external fixationapparatus, each jaw of the jaw pair comprising a curved outer surfaceinterfacing with a curved surface of the socket; a reference componentoffset along the longitudinal axis from the clamp mechanism; and acoupling mechanism arranged between and coupling the clamp mechanism andthe reference component, the coupling mechanism allowing the clampmechanism and the jaw pair to rotate together relative to the referencecomponent about the longitudinal axis, the coupling mechanism comprisinga curved surface interfacing with the curved outer surface of each jawof the jaw pair, and the jaw pair being pivotable within the socket andrelative to the clamp mechanism about a first transverse pivot axis thatis perpendicular to the longitudinal axis.
 2. An articulation device foran external fixation apparatus for treating a patient, the articulationdevice having a longitudinal axis and comprising: a clamp mechanismdefining a socket; an adjustable jaw pair arranged within the socket,the jaw pair being configured to capture a rigid element of the externalfixation apparatus, each jaw of the jaw pair comprising a curved outersurface interfacing with a curved surface of the socket; a referencecomponent offset along the longitudinal axis from the clamp mechanism; acoupling mechanism arranged between and coupling the clamp mechanism andthe reference component, the coupling mechanism allowing the clampmechanism and the jaw pair to rotate together relative to the referencecomponent about the longitudinal axis, and the jaw pair being pivotablewithin the socket and relative to the clamp mechanism about a firsttransverse pivot axis that is perpendicular to the longitudinal axis;and a pair of pins respectively engaging the clamp mechanism and the jawpair, the first transverse pivot axis being defined by a secondlongitudinal axis of the pair of pins and the jaw pair being pivotablerelative to the clamp mechanism about the pair of pins.
 3. Thearticulation device of claim 1, wherein the socket comprises a sphericalsocket and each jaw of the jaw pair comprises a hemispherical jaw. 4.The articulation device of claim 1, wherein the first transverse pivotaxis intersects the longitudinal axis.
 5. The articulation device ofclaim 1, wherein each jaw of the jaw pair comprises an eccentric Gothicarch inner surface configured to capture the rigid element.
 6. Thearticulation device of claim 1, wherein the coupling mechanism comprisesa first component and a second component independent of and disposedbetween the clamp mechanism and the jaw pair and the referencecomponent, the first and second components being rotatable relative toeach other about the longitudinal axis.
 7. The articulation device ofclaim 6, wherein the jaw pair is pivotable about the first transversepivot axis relative to the respective first and second components. 8.The articulation device of claim 6, wherein the first component andsecond component each have a facing surface disposed to face each otherand cooperatively restrict rotational movement of the first componentrelative to the second component when the articulation device isclamped.
 9. The articulation device of claim 8, wherein the firstcomponent comprises a first curved surface opposing the first facingsurface and interfacing with the curved outer surface of each jaw of thejaw pair.
 10. The articulation device of claim 1, wherein the clampmechanism, the jaw pair, and the rigid element comprise a first clampmechanism, a first adjustable jaw pair, and a first rigid element of theexternal fixation apparatus, respectively, and wherein the referencecomponent comprises: a second clamp mechanism defining a second socket;and a second adjustable jaw pair arranged within the second socket, thesecond jaw pair being configured to capture a second rigid element ofthe external fixation apparatus, each jaw of the second jaw paircomprising a second curved outer surface interfacing with a third curvedsurface of the second socket.
 11. The articulation device of claim 10,wherein the coupling mechanism is arranged so that the second clampmechanism and the second jaw pair are rotatable together about thelongitudinal axis relative to the first clamp mechanism and the firstjaw pair, the coupling mechanism comprising a curved surface interfacingwith the second curved outer surface of each jaw of the second jaw pair.12. The articulation device of claim 11, wherein the second jaw pair ispivotable within the second socket and relative to the second clampmechanism about a second transverse pivot axis that is perpendicular tothe longitudinal axis.
 13. The articulation device of claim 10, furthercomprising a locking mechanism structurally configured to lock therelative orientation of the first clamp mechanism and the first jaw pairto the second clamp mechanism and the second jaw pair.
 14. Thearticulation device of claim 1, wherein the coupling mechanism comprisesa threaded collar configured to act as a turnbuckle to pull the jaw pairtogether when tightened.
 15. The articulation device of claim 1, furthercomprising a spring element interposed between the jaws of the jaw pairand biasing the jaw pair in a closed position to capture the first rigidelement.
 16. An articulation element for an external fixation apparatusfor treating a patient, the articulation element having a longitudinalaxis and comprising: a first clamp mechanism defining a first socket inwhich a first adjustable jaw pair is arranged, the first jaw pair beingconfigured to capture a first rigid element of the external fixationapparatus, the first jaw pair being pivotable relative to the firstclamp mechanism about a first transverse pivot axis that isperpendicular to the longitudinal axis, and each jaw of the first jawpair comprising a curved outer surface interfacing with a curved surfaceof the first socket; a second clamp mechanism defining a second socketin which a second adjustable jaw pair is arranged, the second clampmechanism being offset along the longitudinal axis from the first clampmechanism, the second jaw pair being configured to capture a secondrigid element of the external fixation apparatus, the second jaw pairbeing pivotable relative to the second clamp mechanism about a secondtransverse pivot axis that is perpendicular to the longitudinal axis;and a coupling mechanism arranged between and coupling the first andsecond clamp mechanisms such that the first clamp mechanism and thefirst jaw pair can rotate together relative to the second clampmechanism and the second jaw pair about the longitudinal axis, thecoupling mechanism comprising a first curved surface interfacing withthe curved outer surface of each jaw of the first jaw pair.
 17. Thearticulation element of claim 16, wherein: the first socket comprises afirst spherical socket and each jaw of the first jaw pair comprises afirst spherical jaw pair; and the second socket comprises a secondspherical socket and the second jaw pair comprises a second sphericaljaw pair.
 18. The articulation element of claim 16, wherein the couplingmechanism comprises a first component and a second component independentof and disposed between the first and second clamp mechanisms, the firstand second components being rotatable relative to each other about thelongitudinal axis.
 19. The articulation element of claim 18, wherein thefirst component and second component each have a facing surface disposedto face each other and cooperatively restrict rotational movement of thefirst component relative to the second component when the articulationelement is clamped.
 20. The articulation element of claim 19, wherein:the coupling mechanism comprises a second curved surface interfacingwith each jaw of the second jaw pair; the first component comprises thefirst curved surface of the clamping mechanism and the first curvedsurface opposes the first facing surface; and the second componentcomprises the second curved surface of the clamping mechanism and thesecond curved surface opposes the second facing surface.
 21. Thearticulation element of claim 16, wherein the coupling mechanismcomprises a threaded collar configured to act as a turnbuckle to pull atleast one of the first jaw pair and the second jaw pair together whentightened.
 22. The articulation element of claim 16, further comprising:a first spring element interposed between the jaws of the first jaw pairand biasing the first jaw pair in a closed position to capture the firstrigid element; and a second spring element interposed between the jawsof the second jaw pair and biasing the second jaw pair in a closedposition to capture the second rigid element.
 23. The articulationelement of claim 16, wherein each jaw of the second jaw pair comprises acurved outer surface interfacing with a curved surface of the secondsocket and wherein the coupling mechanism comprises a second curvedsurface interfacing with the curved outer surface of each jaw of thesecond jaw pair.
 24. An articulation element for an external fixationapparatus for treating a patient, the articulation element having alongitudinal axis and comprising: a first clamp mechanism defining afirst spherical socket in which a first adjustable pair of hemisphericaljaws are arranged, the first pair of jaws defining an eccentricallyarranged passage through which a first rigid element of the externalfixation apparatus can be received and captured, and the first pair ofjaws being pivotable relative to the first clamp mechanism about a firsttransverse pivot axis that is perpendicular to the longitudinal axis; asecond clamp mechanism offset along the longitudinal axis from the firstclamp mechanism; and a coupling mechanism arranged between and couplingthe first and second clamp mechanisms such that the first clampmechanism and the first jaw pair can rotate together relative to thesecond clamp mechanism and the second jaw pair about the longitudinalaxis, the coupling mechanism comprising a spherical surface interfacingwith a spherical outer surface of each jaw of the first pair of jaws.25. The articulation element of claim 24, wherein the coupling mechanismcomprises a threaded collar configured to act as a turnbuckle to pullthe first pair of jaws together when tightened.
 26. The articulationelement of claim 24, further comprising a spring element interposedbetween the jaws of the first pair of jaws and biasing the first pair ofjaws in a closed position to capture the first rigid element.